Thermostat



May 18, 1943 B. E. SHAW THERMOSTAT Filed June so, 1941 INVENTOR.fiuribwfi? 5 720111 BY 1? 1 w Patented May 1?, 1943 ZEN? GFFICETHERMGSTAT of Iowa mplication June 30, 1941, No. 469,428

(Cl. Zita-139) 9 Jiainis.

My present invention relates to a room thermostat having an adjustingdial provided with an off position and an on position.

One object of my invention is to provide a thermostat wherein agraduated dial may be used for adjusting the range of the thermostat,but at, opposite limits of movement of the dial the thermostat is setfor a sudden decrease and increase, respectively, in the temperatures towhich it is adjusted.

A further object is to provide means at one of these limits to serve asa stop for the switch arm to positively prevent it from assuming aclosed circuit position.

Still another object is to provide a room thermostat in which the onposition is truly an on position only until such time as the thermostatis subjected to an excessively high temperature, whereupon thethermostat opens.

With these and other objects in view, my invention consists in theconstruction, arrangement and combination of the Various parts of mydevice whereby the objects contemplated are attained, as hereinaftermore fully set forth, pointed out in my claims and illustrated in theaccompanying drawing. Although the invention is susceptible of a varietyof embodiments, it is unnecessary to fully describe and illustrate morethan one in order to give a full understanding of the invention bothfrom its structural and functional stand-points. Accordingly, I haveillustrated a preferred and desirable embodiment of the invention in theaccompanying drawing, in which:

Figure 1 is a front elevation of a thermostat embodying my invention,the cover thereof being removed;

Figure 2 is a side elevation of Figure 1 showing the cover in section,and

Figure 3 is a View similar to Figure 1 showing the thermostat in adifferent position.

On the accompanying drawing, I have used the reference numeral iii toindicate a thermostat base. A stud i2 is mounted in the base it and onthe stud I pivotally mount a bell crank lever I3. The bell crank leverl3 has an upstanding arm I4 bent back toward the stud i2 at its upperend to form a perforated ear l5, also pivoted on the stud. A coiledbimetal element l6 has one end secured to the vertical part it of thelever An adjusting dial ii is rotatable on a stud i3 mounted in the baseiii. The dial Ii carries a cam having a spiral face It, a lobe and adepression 21. The lever l3 carries an adjusting screw 22 to coact withthe cam C. A spring 23 is coiled around the stud I2 and has one end 2!:located in the base Iii. Its other end is hooked as at 25 to coact withthe lever l3 and thereby bias it in a clockwise direction to retain theadjusting screw 22 in engagement with the cam C. The bimetal element 16carries a switch arm 26 provided with a contact 27. The contact 21 isadapted to cooperate with a stationary contact 28 carried by a bracket29. A horseshoe magnet 38 cooperates with an armature portion SI of theswitch arm 26 to alford snap action.

The bell crank lever l3 carries a second adjusting screw 32 adapted attimes to coact with the bimetal element i6, as shown by its dottedposition in Figure 1. The stud 18 has a pointer 33 carried thereby tocooperate with the graduation marks and the indicia on and off of thedial IT. A cover 34 is provided for the thermostat mechanism on the baseIii. Th cover 35 may carry a mercury column 35, if desired, forindicating actual room temperatures. The cover 34, together with thebase l0, constitute a casing for the thermostat, and air may circulateup through the casing by entering openings 35 at the bottom of the cover34 and issuing from openings 31 at its top. Such air, in passing throughthe cover, efiects coiling or uncoiling of the bimetal element 16depending on whether the temperature lowers or rises.

Practical operation In the operation of my thermostat, the dial I! maybe adjusted anywhere from to which will cause the spiral portion [9 ofthe cam C to gradually swing the bell crank lever l3, thereby coiling oruncoiling the bimetal element It to make it control the switch contactsat different temperatures. When the dial I1 is adjusted to one extremeposition, indicated as Off in Figure 1, the cam lobe 20 will engage theadjusting screw 22, thus causing the supporting arm [3 to be suddenlyadjusted to an extreme low temperature position. Such position, forinstance, might be as low as 25 below zero before the switch contactswould engage. Thus the temperature afiecting the bimetal element 16 maygo extremely low Without imposing any strains on the bimetal element.

If, however, it is desirable to have the switch positively insuredagainst closing of the contacts at such low temperature, the adjustingscrew 32 may be set as illustrated, so that when the temperatureapproaches the low extreme it will stop the switch arm, as in the dottedposition of Figure 1.

At the other extreme of adjustment, On, as shown in Figure 3, thebimetal element l6 has been adjusted to an extreme high temperatureposition. For instance, the supporting lever 13 might assume the fullline position illustrated when the notch 2| of the cam C registers withthe adjusting screw 22. The temperature then, might rise, which wouldfirst effect movement of the lever I3 to the dotted position andthereafter, upon continued rise, would swing the switch arm 26 to itsdotted position, thus opening the circuit. Such open circuit conditionmight occur in the neighborhood of 115 on an installation where thefurnace is gas fired. Thus, although the thermostat indicates an onposition rather than an automatic position, as indicated by thegraduations from 40 to 80, it actually has a safety feature in that whenthe temperature around the thermostat becomes exceptionally high, itwill automatically open the switch contacts.

The adjusting dial I! may be limited to its extremebn and ofi positionsas by a stop lug 38 projecting downwardly from the dial into an arcuateslot 39 of the base Ill. The adjusting screws 22 and 32 are provided forfactory adjustment, after which only the dial H is adjusted by the user.

Some changes may be made in the construction and arrangement of theparts of my device with-- out departing from the real spirit and purposeof my invention, and it is my intention to cover by my claims anymodified forms of structure or use of mechanical equivalents which maybe reasonably included within their scope without sacrificing any of theadvantages thereof.

I claim as my invention:

1. A thermostat of the character described comprising a movable switchmember, a thermostatic element operating said switch member, anadjustable support for said thermostatic element, manually operablemeans for moving said support to adjust the switch member throughout apredetermined range and adapted when the means is moved to one extremeposition to hold said switch member in open circuit position againstclosing except at an exceptionally low temperature, and stop means tostop said switch arm at a position short of closed circuit position whensaid means is at said extreme position, said dial, at its oppositeextreme position, holding said switch member closed until only anexceptionally high temperature opens it.

2. A thermostat of the character described comprising a movable switchmember, a thermostatic element operating said switch member, anadjustable support for said thermostatic element, manually operablemeans for moving said support and thereby said thermostatic element toadjust the switch member throughout a predetermined range and adaptedwhen the means is moved to one extreme position to hold said switchmemher in open circuit position against closing except at anexceptionally low temperature well beyond such range, said manuallyoperable means, at its opposite extreme position, holding said switchmember closed until only an exceptionally high temperature opens it.

3. A thermostat comprising a casing, a movable switch member, athermostatic element carrying said switch member, an adjustable supportfor said thermostatic element, manually operable means for moving saidsupport to adjust the switch member including a dial projecting from thecasing, a lever connected with said thermostatic element, a cam carriedby said dial and coacting with said lever and adapted when the dial ismoved to one extreme position to suddenly move the lever and therebyhold said switch member in open circuit position against closing exceptat an exceptionally low temperature, said dial, at its opposite extremeposition, suddenly positioning said switch member in its closed circuitposition under such tension of said thermostatic element as to permitthe thermostatic element to open the switch only at an exceptionallyhigh temperature.

4. In a thermostat, a movable switch member, a thermostatic element foroperating said switch member, an adjustable support for saidthermostatic element, means for moving said support to adjust the switchmember, said thermostatic element, when said means is moved into oneextreme position thereof, suddenly assuming a position that permits saidswitch member to function only after an appreciable change intemperature beyond the limit of range adjustment of said means.

5. A thermostat comprising a pair of switch contacts, a thermostaticelement normally operable to move one of said contacts relative to theother in response to changes in temperature, manually operable cam meansoperatively associated with said element to adjust the movable contact,said cam means having a sudden change in contour to coast with saidelement and hold said contacts spaced from each other until anexceptional change in the temperature affecting said element takesplace.

6. In a room thermostat of the character disclosed, a temperatureresponsive element, switch contacts controlled thereby, cam means foradjusting said temperature responsive element to secure different rangesof temperature responsive for the operation thereof, said cam meanshaving a sudden change in contour to adjust said temperature responsiveelement to an extreme low temperature position at one extreme positionof adjustment, said cam means, at the other extreme position ofadjustment, having a second sudden change in contour to close saidswitch and permit its opening in response to only an exceptionally hightemperature affecting said temperature responsive element,

7. In a room thermostat, a supporting arm pivotally mounted, atemperature responsive element mounted thereon, a switch arm carried bysaid temperature responsive element, switch contacts under control ofsaid switch arm, a cam for pivotally adjusting said supporting armgradually throughout a predetermined range of movement of the cam andthereby changing the temperature to which said temperature responsiveelement responds in controlling said switch contacts from one positionto another, means biasing said supporting arm toward said cam, said camhaving a lobe at one extreme position and a depression at its otherextreme position to eiiect respe tively a sudden low temperatureadjustment of said temperature responsive element and a sudden hightemperature adjustment of said temperature responsive element withuniform rotation of said cam at its extreme limits of movement, wherebyat one extreme the switch tends to close only at an exceptionally lowtemperature position, the other limit of adjustment of the cam effectingresponse of said temperature responsive element to open the switch onlyat an exceptionally high temperature.

8. In a thermostat of the class described, a

supporting arm pivotally mounted, a temperature responsive elementmounted thereon, a switch arm carried by said temperature responsiveelement, switch contacts under control of said switch arm, means forpivotally adjusting said supporting arm and thereby said temperatureresponsive element throughout a predetermined range, means at the endsof such range for effecting relatively quick adjustment of saidtemperature responsive element to low and high temperaturesrespectively, and means carried by said supporting arm and constitutinga stop for said switch arm in a position where said contacts areslightly separated when said supporting arm is adjusted to its extremelow temperature position.

9. In a thermostat of the character disclosed,

a base, a supporting arm pivotally mounted thereon, an adjusting screwcarried by said supporting arm, a cam rotatable on said base having aspiral cam surface terminating at its respective ends in a lobe and adepression, said cam surface, lobe and depression being coactable withsaid supporting arm to effect sudden changes in the angle of thesupporting arm in opposite directions at the limits of rotary movementof said cam, a spring biasing said supporting arm to engage said cam, acoiled bimetallic element mounted on said supporting arm, a switch armcarried thereby, switch contacts controlled by said switch arm, andmeans carried by said supporting arm and having an adjusting screwserving as a stop for said switch arm to hold the same in apredetermined open circuit position when said cam is adjusted to one ofits extreme positions.

BURTON E. SHAW.

